Oily sludge has been classified as hazardous waste because of its complex composition， high stability and difficult treatment. At present， the treatment technologies of oily sludge include landfill， solvent extraction， thermochemical cleaning， ultrasonic assisted treatment and biological treatment. Among them， the thermochemical cleaning technology has the advantages of easy operation and high reliability， and the key technology lies in the selection of cleaning agent. Different types of single cleaning agents are introduced， including inorganic sal cleaning agents， chemical surfactants and biological surfactants. This paper classifies and summarizes the compound of different types of single cleaning agents， and focuses on the mechanism of the compound of non?ion?anionic surfactant， non?ion?non?ionic surfactant， alkaline inorganic salt?surfactant and biological surfactant. Based on this， the development direction of thermochemical cleaning agent is prospected in order to improve the cleaning effect of oily sludge.